Stacked-type potentiometric solid-state CO2 gas sensor

A Li-ion based stacked-type potentiometric solid-state (S-PSS) sensor was designed and fabricated to detect carbon dioxide (CO2) on an alumina substrate in an indoor environment using mass production techniques. This design can reduce 70% of the active area compared to a planar-type potentiometric solid-state (P-PSS) sensor, as a reference material is not required. All deposition materials used in the sensor were screen-printed except for the electrolyte, which was deposited using thermal evaporation. The prepared materials were characterized through an X-ray diffraction analysis and scanning electron microscopy. The gas response characteristics of the S-PSS and P-PSS were examined a temperature range of 350–500 °C and for CO2 gas concentrations of between 16 and 5000 ppm. The S-PSS sensor showed a response of 40–90 mV/dec, which is similar to the P-PSS sensor performance at the same operating temperatures. The response and recovery times of the S-PSS were about 2 and 4 s, respectively. Repeated measurements showed a very good consistency of within 5 mV in a full measurement range.